Applicant is a coinventor of a weight-based article theft detection system and product display rack which is disclosed in U.S. Pat. No. 4,819,015, and assigned to the assignee of the present invention. In its original form, the invention of the '015 Patent has been embodied in a large-scale display rack for cartons of cigarettes. Applicant has also developed low-profile weight sensors and a self-calibrating control system which are particularly suited for implementation in small-scale anti-theft product racks, such as counter top displays used in retail stores, as well as other small-scale article storage systems in which it is desired to monitor input and removal of articles from the storage system. These sensors and the self-calibrating control system are disclosed in applicant's copending application, Ser. No. 07/467,516, filed Jan. 18, 1990. In large-scale applications, the control system typically can be supplied power from existing A.C. electrical outlets, or can otherwise be connected into the existing electrical distribution system without undue inconvenience or expense. However, in the case of small-scale applications, such as countertop displays, for example, it is impractical or unacceptable to the owner of the display to have power lines running from the location of the display to the electrical distribution system provided in the display owner's premises.
The control system for small-scale applications is thus advantageously powered by a self-contained power source. Further, in order to be commercially practical, both the antitheft system and its power supply must be as inexpensive as possible, and the power supply should require only minimal maintenance. These requirements make a low voltage, low power consumption, battery powered control system advantageous. However, because the weight measurements on which applicant's theft detection system is based advantageously should be high resolution and noise free measurements, the choices of suitable weight sensors and signal processing circuitry which also satisfy the low power consumption requirements for a practical system are constrained.